Top Voted Answer

Once you get all 7 Fell Arms, go to Aurnion (If you don't know where that is, you will)..And you'll get a scene.

Then finish off the final boss (His 3rd form is an extra form) and carry your items over to the next game.

Then your Fell Arms will grow based on how many enemies the respective character kill. I've gone through the game strictly using Yuri as my "Kill Character" and he has over 5000 attack power on the Abyssion.

To get the first fell arms you need to get it at Myorzo (that flying jelly fish city) You get it from the elder(old fart in the odd looking building in the back). You get it when you re visit this city the second time around I believe. Or you leave and then come back in.

If you get all the 7 fell arms the final boss will get a 3rd form. If you dont get them he only goes to the second form. And from what Powerless says you need to use the 7 fell arms BEFORE you finish the game, because the attack of the weapon will be based on however many monsters you kill with it (on ex new game if you carry your items over). I didnt use the 7 fell arms because I had a better weapon, and carried them over thinking they would be awesome greatness only to find out their attack power was 0! what a kick in the vag that was.

Once u have all fell arms go to aurnion for a scene then head to the final boss and kill him but beware since he has a 3rd form which can wipe u out very easily. The 3rd form is unlocked when u have all the fell arms and have viewed the scene in aurnion. Once that is finished just kill as much enemies as u want and your weapon will become stronger.

You have to get all 7 Fell Arms, defeat the final boss' 3rd form, and then continue from the file you just saved after clearing the game. It will reload to the save point just before the final boss. Check your weapons and you will notice the names of the Fell Arms weapons will have an addition to their names, i.e. Abyssion will become Blazor Edge: Abyssion, along with a more radiant look from formula inscriptions running along them.

The status for the unlocked Fell Arms will be zero for every attribute (P. ATK, P. DEF, M. ATK, M. DEF, AGL, LUCK), but for every enemy you have killed up until this point, and any enemy you kill after [REGARDLESS IF YOU HAVE THE FELL ARM EQUIPPED OR NOT], it will increase P. ATK and M. ATK for the Fell Arm by 1 - it just won't show the power increase until you equip it. But keep in mind that whichever character gets the kill, the +1 P. and M. ATK will go to that specific character's unlocked Fell Arm.

So, in a nutshell, if one character has killed 9999+ enemies, then that character's Fell Arm P. ATK and M. ATK will show 9999 when it's equipped.

-And just for overpowered one-shot God attributes, make sure you have Strength 1 - 4, and/or Magic 1 - 4 for mage users, and HP Condition 1 if you have more than 75% HP and HP Condition 2 if you have less than 25% HP, and check your stats again; you will see your Fell Arm's ATK power go beyond 9999. I believe the highest is 10780 for whichever character's specialty in death-dealing happens to be, whether its physical or magic.

To get the SR Lv4+, you need to visit those weird rock formations, the first one being right outside Nordipolica. That will also net you Zadrick, another Fell Arm. You only need visit two as the SR will only power up two more levels.